Three variants on the same question:
If I click "new identity" in Tor Browser to get a new circuit, why does my new circuit sometimes have the same exit relay as the last circuit? Doesn't that hurt my anonymity?
Does clicking "new identity" replace only my exit relay, or does it replace the whole circuit?
What is the difference between clicking "new identity" in Vidalia and clicking it in Torbutton? Which should I use?